has launched a search for its next chief executive after the nation’s largest newspaper publisher by circulation said Wednesday that Robert Dickey plans to retire from his post.

The McLean, Va.,-based company, which publishes USA Today and the Detroit Free Press among newspapers around the country and the U.K., said Mr. Dickey will remain CEO through early May of 2019.

Gannett said Mr. Dickey, 61, may leave earlier if a successor is appointed before then. The company has hired an executive search firm to help it evaluate internal and external candidates.

Mr. Dickey has served as Gannett’s chief executive since June 2015, a role he assumed after the company split its newspaper publishing business from its broadcast television stations. Prior, Mr. Dickey had served as president of Gannett’s local publishing division.

During his tenure as CEO, Gannett sought to adjust to a fast-shifting environment for news publishers amid declines in print circulation. The company acquired digital-media assets, such as software company WordStream, which provides subscriptions to digital-marketing services, and SweetIQ, a provider of location and reputation management software.

The company also purchased news organizations, building what Mr. Dickey has called the “largest local-to-national media network” in the country. One significant deal was its 2016 takeover of Journal Media Group, the owner of the Milwaukee Journal Sentinel.

Gannett had also considered buying the publisher of the Chicago Tribune, then known as Tronc, but eventually backed off that effort.

“With the support of the nearly 17,000 employees across the company, we have created an organization well positioned to thrive in the years to come,” Mr. Dickey said in prepared remarks.

Similar to other newspaper publishers, the next leader at Gannett will face the challenge of finding new sources of revenue, as the company’s biggest sales generator—advertising—falls. During the first nine months of 2018, revenue from that business fell 7% from the prior year to $1.23 billion. Overall, sales were down 6% to $2.17 billion.

But the company was able to lift profit over that time frame to 25 cents a share, from 18 cents a share, as it reduced expenses.